Interventional radiology procedures are becoming more prevalent for the detection and treatment of many diseases and injuries. Often an interventional radiology procedure involves the viewing of a catheter, or needle, as it is directed into a desired position within the body. Catheter based medical procedures are commonplace and include such medical treatments as balloon angioplasty, laser ablation, the installation of stints and many other valuable treatments. In such medical procedures the progress of the catheter is typically monitored, within a patient's body, by an X-ray fluoroscope imaging system.
During a catheterization procedure, physicians and technicians need to position themselves next to the patient, in order to control the catheter. The overall X-ray exposure to such medical personnel can be higher than the X-ray exposure to the patient because medical personnel may do several X-ray fluoroscopic procedures in a single day and receive multiple dosages of X-ray radiation. For example, neuroangiographic procedures to repair an aneurysm or malformation may take as long as ten hours, during which the patient and physician are exposed to X-ray radiation much of the time. If the physician performs several such procedures a year, the physician quickly may exceed the recommended maximum dosage of radiation. The results of this potential for overexposure has been for highly trained physicians and other technical medical personnel to reduce their work load or to not wear their radiation monitor. Similarly, concern over overexposure may cause a physician to hurry a procedure, thus increasing the chances of making a mistake.
One way to reduce X-ray exposure from fluoroscopy is to use various shielding techniques. Staff can be protected with lead aprons, imaging chain canopies, lead gloves, and eye shields. Patients can be protected with gonad shields, etc. Many of these techniques are not often used because they interfere with the clinical procedure in one way or another.
In X-ray fluoroscopy it is well known that the dosage of the X-ray radiation is inversely proportional to the quantum noise in the viewed image. Prior art methods of X-ray dose reduction have addressed lowering the rate of dosage. For example, a nominal operational rate for X-ray fluoroscope is 30 frames/sec which may result in an exposure of approximately 10R/min skin dose. Prior art methods have attempted to reduce exposure by reducing the operational rate, for example, from 30 frames/sec. to 15 frames/sec. Such techniques have not been successful since a reduced frame rate necessitates an increased dosage rate per frame to minimize the quantum noise, the net result being no significant reduction in exposure.
Other techniques for reducing the dosage of X-ray radiation include operating the fluoroscopy imaging system in a zoom mode; in other words, limiting the X-ray radiation to a small region and electronically magnifying that region to form the entire viewed image. Zoom mode imagery is not popular among some medical personnel because the zoomed image only permits a physician to view a small segment of a patient's body. Such a limited view makes it difficult for a physician to orient the placement of a catheter in a body, and prevents a physician from anticipating upcoming obstacles in the body until they appear in the zoomed image. In addition, in zoom mode, some X-ray systems increase the X-ray tube output dose such as to maintain a constant level of light output from the image intensifier. In that case, there is no dose saving to the patient.
It is therefore a primary objective of the present invention to provide an apparatus and method for reducing X-ray radiation exposure to both patients and medical personnel without adversely affecting either the area of interest the X-ray fluoroscope procedure is being used to view, or the physician's ability to view the peripheral regions surrounding the area of interest.